7A52合金铸锭粗大化合物研究

Research on coarse compound in 7A52 alloy ingot casting

以7A52合金生产过程中出现的铸造供流漏斗底结物、铸锭粗大化合物、锻件偏析、板材点条状缺陷为研究对象,采用化学成分分析、显微组织观察、显微硬度测试、X射线衍射、扫描电镜及能谱分析、热分析等手段,揭示了合金锻件偏析、板材点条状缺陷与铸锭中粗大化合物之间的联系。研究表明,粗大化合物是由Mn、Cr、Ti等元素偏聚形成的MnAl6、CrAl7、TiAl3等组成的混合组织。液穴温度、中间合金及原料、熔炼工艺等是形成粗大化合物的主要影响因素。提出了Mn、Cr、Ti按标准下限控制、延长熔炼时间、适当提高熔体温度、废料预处理重熔及减小中间合金化合物尺寸等措施,经西南铝业集团公司熔铸厂实践证明,避免了7A52圆铸锭中产生粗大化合物。

Accumulation under casting separating funnel,coarse compounds of ingots,segregation of forging and point-line-shaped defects of plates during production process of 7A52 alloy were investigated by using chemical composition analysis,optical microscopy observation,micro-hardness testing,X-ray diffraction,scanning electron microscopy and thermal analysis.The relationship between the coarse compounds of ingots and segregation of forging or point-line-shaped defects of plates is revealed.The results show that the coarse compounds are mixed structures consist of MnAl6,CrAl7,TiAl3 formed by the segregation of Mn,Cr,Ti.The main influence factor of the coarse compound formation is the temperature field,intermediate alloy and casting process parameter.The measures of controlling the amount of Mn,Cr and Ti based on lower limit of standard,increasing smelting time,raising melt temperature during fusion casting,pretreatment and re-melting of scraps from charge materials;and reducing the size of intermediate alloys were put forward.By adopting the above-mentioned measures in Southwest Aluminum Company,the coarse compounds are rarely found again in 7A52 alloy ingots.